In any system of digital data communications between data processing sites a few words or characters make up the majority of the transmitted message. Using a remote processor display panel as an example, alphabetic and numeric characters are most often displayed. The alphabet and numbers O - 9 represent only 36 of the possible 128 total bit pattern combinations or character format in a seven-level system. The remaining bit pattern combinations make up control characters and various punctuation characters.
Communications line terminals typically operate in a fixed-level; that is, the transmitted characters are all composed of a fixed number of bits: in describing a word or character the term "level" is synonymous with the term "bit". For example, a eight-level communications line terminal is one in which the character length will always be 8 bits. Accordingly, irrespective of frequency of use all characters are of a fixed-level format requiring greater than necessary message block transmission times. The present invention utilizes a variable character format that is modified for each application such that the most frequently used characters are transmitted in a shortened character format for minimizing total message block transmission time.